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Re^2: Memory usage of a "sub" in mod_perl

by diego_de_lima (Beadle)
on May 23, 2008 at 19:33 UTC ( #688198=note: print w/replies, xml ) Need Help??


in reply to Re: Memory usage of a "sub" in mod_perl
in thread Memory usage of a "sub" in mod_perl

Thnaks for all answers, they were quite usefull.

Iīve many circular refs, and now I weakened them, which reduced slightly the memory usage. But still the process grows and donīt free its memory.

100K HTML isnīt a big problem, but some times I have a 10mb ou 30mb structure in memory, which then generates a 3 mb HTML. And thats the problem.

Iīm sure there arenīt circular refs anymore, but system doesnīt reclaims memory. I think this is the normal behavior, and Apache2::SizeLimit is the only solution for this. Am I right?

But I still canīt undestand why it says the sub "end" is eating all this memory! I would understand if it says there is a global variable or something, but why a sub? For example, the perl-stats Memory Usage of the Html::page package says:
128:       undef PV    44 bytes html
129:       undef NULL  24 bytes 0xa7f4cb8
130:       undef PV   37740 bytes Content-type: text/html
Cache-Control: no-cache,no-store,max-age=0
Pragma: no-cache

<html>... ALL MY PAGE HERE 2 MB OF DATA!!!

Why is it still arround? Iīve done a $page->{html} = ''; in the DESTROY method and Iīm sure it was invoked. And, by the way, it has nothing to do with the sub "end". "end" just parses $page->{html}, then flushes it to the browse and then undef $page->{html}. Shouldnīt "undef" be enouth?

Thanks monks!

Diego de Lima
  • Comment on Re^2: Memory usage of a "sub" in mod_perl

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Re^3: Memory usage of a "sub" in mod_perl
by shmem (Chancellor) on May 23, 2008 at 19:53 UTC
    and then undef $page->{html}. Shouldn't "undef" be enough?

    That depends upon what that hash entry actually is. If it is a reference (or something containing a reference) to data which is held elsewhere, you just clear that slot from the reference, but not the referenced data.

    Consider:

    perl -le '$foo = "bar"; $h->{foo} = \$foo; undef $h->{foo}; print "foo + :$foo:"' foo :bar:

    which is different to

    perl -le '$foo = "bar"; $h->{foo} = \$foo; undef ${$h->{foo}}; print " +foo :$foo:"' foo ::

    where the referenced data is cleared.

    --shmem

    _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                                  /\_¯/(q    /
    ----------------------------  \__(m.====·.(_("always off the crowd"))."·
    ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
      In my case, $page->{html} is a simple string, like:
      $page->{html} = '...ALL HTML HERE 2 MB OF PLAIN TEXT...';
      
      So, isnīt undef $page->{html} enought?

      Diego de Lima
        Yes, that should do - but only if there's no reference to that string elsewhere.

        --shmem

        _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                                      /\_¯/(q    /
        ----------------------------  \__(m.====·.(_("always off the crowd"))."·
        ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
Re^3: Memory usage of a "sub" in mod_perl
by perrin (Chancellor) on May 23, 2008 at 20:08 UTC
    If you run the exact same request multiple times and the process size grows every time, you have a leak, probably a circular reference. If it stops growing but remains at the larger size, that is completely normal and the only way to avoid it is to structure your code so that it doesn't need to have all the data in memory at once.

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